A Study of Energy Saving in Customizable Processors

Embedded systems are special purpose systems which perform predefined tasks with very specific requirements like high performance, low volume or low power. Most of the time, using a general purpose processor for such systems results in a design which is poor to meet the application specific requirement. On the other hand, ASIC design cycle is too costly and too slow for the embedded application market. Recent development in configurable processors significantly improved the performance metrics of a general purpose processor by coupling it with an application specific hardware. Although there has been a large amount of work in the literature to improve the performance and automation of such designs, little has been done to examine the power consumption of a system coupled with an application specific functional unit. Monitoring this power behavior may provide new directions in the ASIP design. We augmented wattch (a power simulator based on SimpleScalar) with a model of the power consumption of functional units (using a combination of RTLand gate-level power modeling). Our results show that a well-designed custom instruction set may reduce register and memory accesses, and hence the overall power consumption of an embedded system.